Abstract

Picornaviruses are associated with serious diseases in humans and other animals, and they comprise one of the largest families of viral pathogens. For example, the common cold, poliomyelitis, foot-and-mouth disease and hepatitis can be caused by these viruses. They are among the smallest RNA-containing animal viruses (1–3). Their molecular weight is a round 8.5 x 106 and they contain about 30% by weight RNA. Their external diameter is roughly 300 Å and they form icosahedral shells. Picornaviridae have been subdivided into four genera on the basis of their buoyant density, pH stability and sedimentation coefficients: enterovirus (e . g . polio, hepatitis A and coxsackie viruses), cardiovirus (e .g . encephalomyocarditis and Mengo viruses), aphthovirus (e.g. foot-and-mouth disease virus) and rhinovirus . They differ also in the number of known serotypes. For instance there are three known serotypes for polioviruses, seven for foot-and-
mouth disease viruses (FMDV) and at least 89 for human rhinoviruses (HRV). Accordingly, it has been possible to produce effective vaccines for poliomyelitis and, with greater difficulty , for foot-and-mouth disease, but
not for the common cold.

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